Processing for high permeability silicon steel comprising copper

ABSTRACT

A process for producing silicon steel having a cube-on-edge orientation and a permeability of at least 1850 (G/Oe) at 10 oersteds, which includes the steps of: annealing silicon steel prior to a final cold roll at a temperature of from 1400* to 2150*F; cooling the steel from a temperature below 1700*F and above 750*F to a temperature at least as low as 500*F at a rate which is faster than a still air cool and from its maximum annealing temperature to the temperature below 1700*F and above 750*F at a rate which is no faster than a still air cool; and cold rolling the steel at a reduction of at least 80 percent.

United States Patent Salsgiver et a1.

' [111 3,855,020 [451 Dec. 17, '1974 [5 PROCESSING FOR HIGH PERMEABILITY SILICON STEEL COMPRISING COPPER [75] Inventors: James A. Salsgiver, Sarver; Frank A.

Malagari, Freeport, both of Pa.

[73] Assignee: Allegheny Ludlum Industries, Inc.,

Pittsburgh, Pa.

[22] Filed: May 7, 1973 [21] Appl, No.: 357,974

[52] US. Cl. 148/112, 75/123 L, 148/31.55,

[51] Int. Cl. H011 1/04 [58] Field of Search 148/112, 111, 110, 31.55, 148/113; 75/123 L [56] References Cited UNITED STATES PATENTS 1,919,983 7/1933 Morrill 148/112 2,209,686 7/1940 Crafts 148/31.55

3,151,005 9/1964 Alworth et a1 148/111 3,159,511 12/1964 Taguchi et a1. 148/111 3,266,955 8/1966 Taguchi et a1. 148/111 3,287,184 11/1966 Koh 1 148/113 3,632,456 l/1972 Sakakura et a1. 148/111 3,671,337 6/1972 Kumai et a1. 148/112 3,764,406 10/1973 Littmann 148/111 3,770,517 11/1973 Gray et al. 148/111 OTHER PUBLICATIONS Primary Examiner-Walter R. Satterfield Attorney, Agent, or F irm -Vincent G. Gioia; Robert f, Drapkin [5 7] ABSTRACT A process for producing silicon steel having a cubeon-edge orientation and a permeability of at least 1850 (6/0,) at 10 oersteds, which includes the steps of: annealing silicon steel prior to a final cold roll at a temperature of from 1400 to 2150F; cooling the steel from a temperature below 1700F and above 750F to a temperature at least as low as 500F at a rate which is faster than a still air cool and from its maximum annealing temperature to the temperature below 1700F and above 750F at a rate which is no faster than a still air cool; and cold rolling the steel at a reduction of at least 80 percent.

18 Claims, N0 Drawings The present invention relates to a process for producing electromagnetic silicon steel having a cube-on-edge orientation and a permeability of at least 1850 (G/O,.) at 10 oersteds. Oriented silicon steels containing 2.60 to 4.0 percent silicon are generally produced by processes which involve hot rolling, av double cold reduction, an anneal before each cold roll and a high temperature texture anneal. Characterizing these steels are permeabilities at 10 oersteds of from about 1790 to 1840 (Ci/ In recent years a number of patents have disclosed silicon steels with permeabilities in excess of 1850 (6/0 at 10 oersteds. Of these, U.S. Pat. Nos. 3,287,183, 3,632,456 and 3,636,579 appear to be the most interesting from a processing standpoint. U.S. Pat. No. 3,287,183 which issued on Nov. 22, 1966 reveals that a steel composed of specific amounts of carbon, silicon, aluminum, sulfur and iron could be processed into a high permeability silicon steel by cold rolling from to 40 percent annealing at a temperature of from l742 to 2l92F so as to precipitate AlN, cold rolling from 81 to 95 percent, decarburizing and final texture annealing. More recently, similar processing for similar alloys was disclosed in U.S. Pat. Nos. 3,632,456 and 3,636,579, which respectively issued on Jan. 4, 1972, and Jan. 25, 1972. Each of these patents refer to cooling rates following the anneal in which MN is precipitated. U.S. Pat. No. 3,632,456 anneals a hot rolled band at a temperature of from 1382 to 2l92F, depending upon its silicon content, rapidly cools the an nealed band and then proceeds to subject it to at least two cold rollings. U.S. Pat. No. 3,636,579 anneals steel containing 2.5 to 4 percent silicon at a temperature of from l742 to 2l92F, quenches it from said temperature to a temperature at least as low as 752F and then cold rolls it. I

Described herein is another, and improved method for producing silicon steel having a cube-on-edge orientation and a permeability of at least 1850 (G/O at oersted from steel of a particular chemistry. The method includes the steps of: annealing silicon steel prior to a final cold roll at a temperature of from l400 to 2150F; cooling the steel from a temperature below 1700F and above 750F to a temperature at least as low as 500F at a rate which is faster than a still air cool and from its maximum annealing temperature to the temperature below 1700F and above 750F at a rate which is no faster than a still air cool; and cold rolling the steel at a reduction of at least 80 percent. It differs from and is contradictory to the methods of heretofore referred to U.S. Pat. Nos. 3,287,183, 3,632,456 and 3,636,579 in that: U.S. Pat. No. 3,287,183 does not relate to cooling rates; U.S. Pat. No. 3,362,456 calls for an anneal and two cold rollings subsequent to the anneal aimed at precipitating AlN and the rapid cool which occurs thereafter; and both U.S. Pat. Nos. 3,632,456 and 3,636,579 refer to rapid cools from a temperature in excess of l742F, for steels containing at least 2.5% Si. Moreover, the chemistry of the steel being processed in accordance with the present invention differs from that being processed in said heretofore referred to patents.

It is accordingly an object of the present invention to provide a process for producing electromagnetic silicon steel having a cube-on-edge orientation and a permeability of at least l850 (G/O at l0.oersteds.

The present invention provides a method for producing silicon steel having a cubeaon-edge orientation and a permeability of at least 1850 (6/0 and preferably at least 1900 (G/O at 10 oersteds. Involved therein are the steps of: preparing a melt of silicon steel having, by weight, up to 0.07% carbon, from 2.60 to 4.0% silicon, from-0.03% to 0.24% manganese, from 0.01 to 0.07% sulfur, from 0.015 to 0.04% aluminum, up to 0.02% nitrogen, and from 0.1 to 0.5% copper; casting the steel; hot rolling the steel into a hot rolled band; subjecting the steel to at least one cold rolling and generally two; subjecting the steel to a final annealing prior to the final cold rolling; decarburizing the steel; and

final texture annealing the steel. Also included, and significantly so, are the specific steps of: carrying out the final anneal prior to the final cold rolling at a temperature of from l400 to 2150F for a period of from l5 seconds to 2 hours; cooling the steel from a temperature below 1700F and above 750F to a temperature at least as low as 500] at a rate which is faster than a still air cool and fromits maximum annealing temperature to the temperature below 1700F and above 750F at a rate which is no faster than a still air cool; and cold rolling the cooled steel at a reduction of at least percent. Preferred conditions include annealing at a temperature of from l800 to 2125F, cooling at a rate faster than a still air cool from a temperature below 1600F and above 1200F, and cold rolling at a reduction of at least percent. No critically is placed upon the means for obtaining a cooling rate faster than a still air cool. Illustrative means are gaseous streams and liquid quenching mediums. For purposes of definition, still air. cools include those wherein the steel is cooled in a static atmosphere as well as those wherein there is relative motion between the atmosphere and the steel, as in a continuous processing line, so long as there is no deliberate intention to cause the motion for cooling purposes. Moreover, for purposes of definition, all gaseous atmospheres are considered to have the same cooling effect as air. Hence, all cools are considered to be at a rate no faster than a still air cool unless a liquid quenching medium or forced gaseous atmosphere is employed, and a forced' gaseous atmosphere is one in which motion is deliberately imparted to the atmosphere for cooling purposes.

Melting, casting, hot rolling, cold rolling, decarburizing and final texture annealing do not involve any novel procedure, as far as techniques are concerned, and with regard to them, the invention encompasses all applicable steelmaking procedures. As to the cold rolling, it should, however, be pointed out that several roll passes can constitute a single cold rolling operation, and that plural cold rolling operations exist only when cold rolling passes are separated by an anneal.

' The steel melt must include silicon, aluminum, manganese, sulfur and copper. Silicon is necessary as it increases the steels resistivity, decreases its magnet0- striction, decreases its magnetocrystalline anisotropy and hence decreases its core less. Aluminum, manganese and sulfur are necessary as they form inhibitors which are essential to controlling the steels orientation and its properties which are dependent thereon. More specifically, aluminum combines with nitrogen, in the steel or from the atmosphere to form aluminum nitride, and manganese combines with sulfur to form manganese sulfide and/or manganese copper sulfide; and these compounds act so as to inhibit normal grain growth during the final texture anneal, while at the same time, aiding in the development of secondary recrystallized grains having the desired cube-on-edge orientation. Copper, in addition to possibly forming manganese copper sulfide, is believed to be beneficial in that it is hypothesized that copper can lower the annealing temperature, lower the temperature from which the rapid cool can occur, improve rollability, simplify melting and relax annealing atmosphere requirements. Alloys with more than 0.15 percent copper have been successfully annealed prior to the final cold rolling at temperatures of from l400 to l700F.

A steel in which the process of the present invention is particularly adaptable to consist essentially of, by weight, from 0.02 to 0.07% carbon, from 2.60 to 3.5% silicon, a manganese equivalent of from 0.05 to 0.24% as expressed by an equivalency equation of %Mn (0.1 to 0.25) X %Cu, from 0.0l to 0.5% sulfur, from 0.0 l 5 to 0.04% aluminum, from 0.0030 to 0.0090% nitrogen, from 0.1 to 0.3% copper, balance iron and residuals; and wherein the ratio of manganese equivalent to sulfur is in the range of from 2.0 to 4.75. The steel has its chemistry balanced so as to produce a highly beneficial structure when processed according to the present invention.

Although we are not sure why the annealing and cooling of the present invention is so beneficial, we hypothesize: that the anneal conditions the steel for cold rolling and provides an operation during which inhibitors can form; and that the slow cool to a temperature below 1700F and [or the use of annealing temperatures in the lower part of the annealing temperature range, increase the uniformity in which the inhibitors are distributed, as essentially only ferrite phase is present in the steel at temperatures below l700F, contrasted to the presence of austenite and ferrite phases and different solubilities for the inhibiting elements in each phase 'at somewhat higher temperatures. As discussed above, the primary inhibitors are aluminum nitride and manganese sulfide and/or manganese copper sulfide. No criticality is placed upon the particular annealing atmosphere. Illustrative atmospheres therefore include nitrogen; reducing gases such as hydrogen; inert gases such as argon; air; and mixtures thereof.

The following examples are illustrative of several aspects of the invention.

EXAMPLE 1 Twelve samples (Samples l 12) of silicon steel were cast and processed into silicon steel having a cube-onedge orientation from two heats (l-leats A and B) of BOF silicon steel. The chemistry of the heats, that is Heats A and B, appears hereinbelow in Table I.

TABLE I izing for 2 minutes at 1650F in air, cold rolling to a gage of approximately 88 mils, annealing a 2000F for 5 minutes in nitrogen, cooling by one of three cooling methods (Cooling Methods, 1, I] or Ill), cold rolling to final gage of approximately 12 mils, decarburizing for 2 minutes at l475F in a mixture of nitrogen and wet hydrogen, and final annealing for 8 hours in hydrogen at a maximum temperature of 2150F. Cooling Method I was applied to samples 1, 4, 7 and 10, and is one in which the samples are cooled in a welded box. it is a cool which is slower than an air cool. Samples 1, 4, 7 and 10 took approximately minutes to cool to 750F. Cooling Method [I was applied to samples 2, 5,

8 and 11, and is one in which the samples are furnace cooled to l600F and air cooled therefrom. Furnance cooling to l600F took approximately 20 minutes. Cooling from l740 to l600F took approximately 8 minutes. Cooling Method [II was applied to samples 3,

6, 9 and 12, and is the same as Cooling Method ll with the exception that the samples were brine quenched at l600F. I

Samples 1 12 were tested for permeability and core less. The results of the tests appear hereinbelow in Table II. Results have been broken up into four groups so that only samples from the same heat and'coil are directly compared. Samples l, 2 and 3 are from the same heat and coil and form one group, as do samples 4, 5 and 6, samples 7, Band 9, and samples 10, l l and 12.

From Table ll, it is clear that the processing of the present invention is highly beneficial to the properties of silicon steel having a cube-on-edge orientation. Samples 3, 6, 9 and 12 were annealed in nitrogen for 5 min utes a 2000F, cooled to l600F at a rate slower than a still air cool and cooled from l600F to a temperature.

below 500F at a rate faster than a still air cool; and all had permeabilities in excess of 1900 (6/0,) at 10 0 On the other hand, samples 1, 4, 7'and 10 which were annealed as were samples 3, 6, 9 and 12, but not cooled from a temperature in excess of 750F at a rate faster COMPOSITION (Wt.

Processing for the twelve samples involved soaking at an elevated temperature, for several hours, blooming, hot rolling to a gage of approximately mils, normalthan a still air cool, all had permeabilities less than l850 (6/0 at 10 0 Having permeabilities between the values for samples 3, 6, 9 and 12, and samples 1, 4,

7 and were samples 2, 5, 8 and 11. These samples values for samples 16 and 14 was sample 15. It was anwere annealed as were the other samples,'and cooled l d s were samples 16 and 14, but unlike sample to l600F as were samples 3, 6, 9 and 12, but unlike samples 2, 6, 9 and 12 they were not cooled from l600F at a rate faster than a still air cool. This perme- 5 abilities were high but not as high as those of samples 9 and Samples processed m accordance over, sample 16 had a lower core loss than did sample with the present invention. Moreover, samples 3, 6, 9 15 and Sample 15 had a lower core loss than did and 12 had lower core losses than did samples 2, 5, 8 ple and 11, and samples 2, 5, 8 and 11 had lower core 10 losses than did samples 1, 4, 7 and 10. Of course, all comparisons are made for the respective groups.

16 was not cooled froml475F at a rate faster than a still air cool. The permeability for this sample was high but not as high as that for sample 16, the same processed in accordance with the present invention. More- It will be apparent to those skilled in the art that the novel principles of the invention disclosed herein in various other modifications and applications of the EXAMPLE n same. It is accordingly desired that in construing the Three additional samples (Samples l4 16) of silil5 breadth of the appended claims they shall not be limcon steel were cast and processed into silicon steel havited to the specific examples of the invention described ing a cube-on-edge orientation from a third heat (Heat herein.

C) of BOF silicon steel. The chemistry of the heat, that We claim:

is Heat C, appears hereinbelow in Table Ill. 1. In a process for producing electromagnetic silicon TABLE Ill COMPOSITION (Wt.

Heat C Mn S Si Al Oi N Fe C 0.049 0.094 0.032 2.91 0.036 0.22 0.0046 Bal.

Processing for the three samples involved soaking at steel having a cube-on-edge orientation and a permeaan elevated temperature for several hours, blooming, 3O bility of at least 1850 (6/0,) at 10 oersteds, which prohot rolling to a gage of approximately 92 mils, annealcess includes the steps of: preparing a melt of silicon ing at l 75F f r 1 h r in n g n. ng y n f steel; casting said steel; hot rolling said steel into a hot three methods, cold rolling a final gage of approxi rolled band; subjecting said steel to at least one cold mately .13 mils, decarburizing for 2 minutes at l475F lli bj ti id t el t a final annealing prior in a mixture of nitrogen and Wet hydrogen, and final to the final cold rolling; decarburizing said steel; and nealing for 8 hours in hydrogen at a maximum temperafinal texture annealing said steel; the improvement ture Of The three cooling methods were a furcomprising steps of carrying out aid final anneal L an cool and a brine q Sample 14 prior to the final cold rolling at a temperature of from was furnace cooled, sample 15 was air cooled, and the 1400 to 2150* f a i d f f 15 Seconds to 2 brine quench was applied to Sample hours; cooling said steel from a temperature below Samples 14 16 were tested for Permeablhty and 1700F and above 750F to a temperature at least as core loss. The results of the tests appear hereinbelow low as with a liquid quenching medium or gase connection with specific examples thereof will suggest in Table ous stream and from its maximum annealing tempera- TABLE IV ture to said temperature below 1700F and above 750F at a rate which is no faster than one wherein the Permeability Core Loss steel is cooled in a static atmosphere or in a continuous Sample Hem (at or) (WPP 17 KB) processing line where there is some relative motion be- 14 C Furnace 1651 127 tween the atmosphere and the steel, although the only l5 C Air 1860 0.785 deliberate motion is that imparted to the steel; and cold 16 C Brine Quench 1902 0.708

rolling the cooled steel at a reduction of at least 80 percent; said melt consisting essentially of, by weight, up

From Table IV, it is clear that the processing of the to 0.07% carbon, from 2.60 to 4.0% silicon, from 0.03 present invention is highly beneficial to the properties to 0.24% manganese, from 0.01 to 0.07% sulfur, from of silicon steel having a cube-on-edge orientation, and 0015 I0 004% aluminum P 002% nitrogen, from from Tables II and IV, it is clear that this processing is .1 to 0.5% and the balance iron.

beneficial whether there is only-one cold rolling as in 2- An improvement according to claim 1, wherein Example II or at least two cold rollings as in Example said steel is cooled from a temperature below l600F l. Sample 16 was annealed in nitrogen for 1 hour at and above 1200F to a temperature at least as low as 1475F and cooled therefrom to a temperature below 500F at a rate which is faster than a still air cool and 500F at a rate faster than a still air cool; and had a perfrom its maximum annealing temperature to said temmeability in excess of 1900 (6/0,) at 10 0,.. On the perature below 1600F and above 1200F at a rate other hand, sample 14 which was annealed as was samwhich is no faster than a still air cool.

ple 16, but not cooled from a temperature in excess of 3. An improvement according to claim 1, wherein 750F at a rate faster than a still air cooled from a temid fi l anneal prior tqthe final cold r lli i at a perature in excess of 750F at a rate faster than a still temperature of from l800 to 2l25F.

air cool, had a permeability considerably below 1850 4. An improvement according to claim 3, wherein (G/O,,) at 10 0,. Having a permeability between the said steel is cooled from a temperature below 1'6 O0F i and above l200F to a temperature at least as low as 500F at a rate which is faster than a still air cool and from its maximum annealing temperature to said temperature below l600F and above l200F at a rate which is no faster than a still air cool.

5. An improvement according to claim 1 wherein said steel is cooled to a temperature at least as low'as 500F from a temperature below l700F and above 750F with a gaseous stream.

6. An improvement according to claim 1 wherein said steel is cooled to a temperature at least as low as 500F from a temperature below 1700F and above 750F with a liquid quenching medium.

7. An improvement according to claim 1 wherein said steel is air cooled to said temperature below l7 00F and above 750F.

8. An improvement according to claim 3 wherein said steel is cooled to a temperature at least as low as 500F from a temperature below 1700F and above 750F with a gaseous stream.

9. An improvement according to claim 3 wherein said steel is cooled to a temperature at least as low as 500F from a temperature below l700F and above 750F with a liquid quenching medium.

7 12. An improvement according to claim 1, wherein said steel consists essentially of, by weight, from 0.02 to 0.07% carbon, from 2.60 to 3.5% silicon, a manganese equivalent of from 0.05 to 0.24% as expressed by an equivalency equation of Mn (O.l to 0.25) X Cu, from 0.01 to 0.05% sulfur, from 0.015 to 0.04% aluminum, from 0.0030 to 0.0090% nitrogen, from O.l to 0.3% copper, balance iron and residuals; and wherein the ratio of manganese equivalent to sulfur is in the range of from 2.0 to 4.75.

13. An improvement according to claim 1, wherein the cooled steel is cold rolled at a reduction of at least percent.

14. An improvement according to claim 4, wherein the cooled steel is cold rolled at a reduction of at least 85 percent.

15. An improvement according to claim 1 wherein said final anneal prior to the final cold rolling is applied to a hot rolled band.

16. An improvement according to claim 1 wherein said steel has at least 0.15% Cu' and wherein said final quenching medium. 

1. IN A PROCESS FOR PRODUCING ELECTROMAGNETIC SILICON STEEL HAVING A CUBE-ON-EDGE ORIENTATION AND A PERMEABILITY OF AT LEAST 1850 (G/OE) AT 10 OERSTEDS, WHICH PROCESS INCLUDES THE STEPS OF: ROLLING SAID STEEL INTO A HOT ROLLED BAND; SUBJECTING SAID STEEL TO AT LEAST ONE COLD ROLLING; SUBJECTING SAID STEEL TO A FINAL ANNEALING PRIOR TO THE FINAL COLD ROLLING; DECARBURIZING SAID STEEL; AND FINAL TEXTURE ANNEALING SAID STEEL; THE IMPROVEMENT COMPRISING THE STEPS OF CARRYING OUT SAID FINAL ANNEAL PRIOR TO THE FINAL COLD ROLLING AT A TEMPERATURE OF FROM 1400* TO 2150*F FOR A PERIOD OF FROM 15 SECONDS TO 2 HOURS; COOLING SAID STEEL FROM A TEMPERATURE BELOW 1700*F AND ABOVE 750*F TO A TEMPERATURE AT LEAST AS LOW AS 500*F WITH A LIQUID QUENCHING MEDIUM OR GASEOUS STREAM AND FROM ITS MAXIMUM ANNEALING TEMPERATURE TO SAID TEMPERATURE BELOW 1700*F AND ABOVE 750*F AT A RATE WHICH IS NO FASTER THAN ONE WHEREIN THE STEEL IS COOLED IN A STATIC ATMOSPHERE OR IN A CONTINUOUS PROCESSING LINE WHERE THERE IS SOME RELATIVE MOTION BETWEEN THE ATMOS SPHERE AND THE STEEL, ALTHOUGH THE ONLY DELIBERATE MOTION IS THAT IMPARTED TO THE STEEL; AND COLD ROLLING THE COOLED STEEL AT A REDUCTION OF AT LEAST 80 PERCENT; SAID MELT CONSISTING ESSENTIALLY OF, BY WEIGHT, UP TO 0.70% CARBON FROM 2.60 TO 4.0% SILICON, FROM 0.03 TO 0.24% MANGANESE, FROM 0.01 TO 0.07% SULFUR, FROM 0.015 TO 0.04% ALUMINUM, UP TO 0.02% NITROGEN, FROM 0.1 TO 0.5% AND THE BALANCE IRON.
 2. An improvement according to claim 1, wherein said steel is cooled from a temperature below 1600*F and above 1200*F to a temperature at least as low as 500*F at a rate which is faster than a still air cool and from its maximum annealing temperature to said temperature below 1600*F and above 1200*F at a rate which is no faster than a still air cool.
 3. An improvement according to claim 1, wherein said final anneal prior to the final cold rolling is at a temperature of from 1800* to 2125*F.
 4. An improvement according to claim 3, wherein said steel is cooled from a temperature below 1600*F and above 1200*F to a temperature at least as low as 500*F at a rate which is faster than a still air cool and from its maximum annealing temperature to said temperature below 1600*F and above 1200*F at a rate which is no faster than a still air cool.
 5. An improvement according to claim 1 wherein said steel is cooled to a temperature at least as low as 500*F from a temperature below 1700F and above 750*F with a gaseous stream.
 6. An improvement according to claim 1 wherein said steel is cooled to a temperature at least as low as 500*F from a temperature below 1700*F and above 750*F with a liquid quenching medium.
 7. An improvement according to claim 1 wherein said steel is air cooled to said temperature below 1700*F and above 750*F.
 8. An improvement according to claim 3 wherein said steel is cooled to a temperature at least as low as 500*F from a temperature below 1700*F and above 750*F with a gaseous stream.
 9. An improvement according to claim 3 wherein said steel is cooled to a temperature at least as low as 500*F from a temperature below 1700F and above 750*F with a liquid quenching medium.
 10. An improvement according to claim 3 wherein said steel is air cooled to said temperature below 1700*F and above 750*F.
 11. An improvement according to claim 1, wherein said final anneal prior to the final cold rolling is carried out subsequent to an initial cold rolling.
 12. An improvement according to claim 1, wherein said steel consists essentially of, by weight, from 0.02 to 0.07% carbon, from 2.60 to 3.5% silicon, a manganese equivalent of from 0.05 to 0.24% as expressed by an equivalency equation of % Mn + (0.1 to 0.25) X % Cu, from 0.01 to 0.05% sulfur, from 0.015 to 0.04% aluminum, from 0.0030 to 0.0090% nitrogen, from 0.1 to 0.3% copper, balance iron and residuals; and wherein the ratio of manganese equivalent to sulfur is in the range of from 2.0 to 4.75.
 13. An improvement according to claim 1, wherein the cooled steel is cold rolled at a reduction of at least 85 percent.
 14. An improvement according to claim 4, wherein the cooled steel is cold rolled at a reduction of at least 85 percent.
 15. An improvement according to claim 1 wherein said final anneal prior to the final cold rolling is applied to a hot rolled band.
 16. An improvement according to claim 1 wherein said steel has at least 0.15% Cu and wherein said final anneal prior to the final cold rolling is at a temperature of from 1400* to 1700*F.
 17. An improvement according to claim 16 wherein said steel is cooled to a temperature at least as low as 500*F from a temperature above 750*F with a gaseous stream.
 18. An improvement according to claim 16 wherein said steel is cooled to a temperature at least as low as 500*F from a temperature above 750*F with a liquid quenching medium. 